1. Field of the Invention
The present invention relates to an ink, an ink cartridge and an ink jet recording method.
2. Description of the Related Art
An ink jet recording method is such a recording method that minute droplet of an ink are applied to a recording medium such as plain paper to form an image, and is rapidly spread owing to low price of an apparatus itself and improvement of recording speed. In general, a recorded article obtained by the ink jet recording method is low in fastness properties of an image thereof compared with a silver salt photograph. In particular, when the recorded article is exposed to light, humidity, heat or environmental gas present in air, such as an ozone gas for a long period of time, there is a problem that a coloring material of the recorded article is deteriorated to easily cause change in color tone or fading of the image.
It is difficult to attain, with conventionally known coloring materials provided with Color Index (C.I.) numbers, both an optical density (color developing properties) and fastness properties of an image required of an ink jet ink, and therefore, coloring materials having novel structures are being widely studied. For example, a bisazo compound providing an image having a good optical density and excellent light resistance and ozone resistance is proposed in Japanese Patent Application Laid-Open No. 2004-083903 (Patent Document 1).
Beside, an ink containing 1,5-pentanediol and a humectant such as glycerin, ethylene glycol or ethylene urea is proposed as an ink with improved intermittent ejection stability in Japanese Patent Application Laid-Open No. 2007-039680 (Patent Document 2). Furthermore, an ink containing a specific azo compound to be a magenta coloring material, an acetylene glycol surfactant having an average addition mole number x+y of ethylene oxide groups falling in a range or 0≦x+y≦8.0, and alkanediol is proposed in Japanese Patent Application Laid-Open No. 2011-213845 (Patent Document 3). The ink proposed in Patent Document 3 is described to have good intermittent ejection stability.